The intravenous administration of fluids into the human body is a routine medical procedure, typically one in which a liquid solution containing a nutrient or a drug is allowed to flow under gravity from a container through a flexible, small diameter tubing into the vein of a patient. Since in many cases it is desired that the flow be maintained at a precise low rate over a long period of time, some means for controlling the flow rate must be provided, such means typically being a clamp which deforms the walls of the tubing sufficiently to control the flow rate of the fluid passing therethrough.
A number of different clamps which function in this manner have been used or proposed, ranging from a simple spring-biased clamp capable only of on-off control, to more complex arrangements providing a finer degree of control, as shown in U.S. Pat. Nos. 1,865,012, 2,825,333, 2,954,028, 3,167,085, 3,497,175, 3,612,474 and 3,685,786.
In addition to providing precise control of fluid passing through the tubing with which it is used, particularly at low rates of flow which may be on the order of a few drops per minute, a clamp intended for this purpose desirably possesses a number of other features. The force exerted by the clamping member on the flexible tubing should be applied over a relatively large area of the tubing, so as to avoid creating a permanent set or deformation in the tubing. This is important in order to insure that the tubing, after being compressed or deformed by the clamp for a substantial period of time, will tend to resume its original shape when the clamp is loosened. Since the pressure of the flowing fluid is generally very small, the natural resiliency of the tubing must be relied on to ensure that the tube will expand to permit a greater flow as the clamping force exerted by the clamp is decreased. If the clamping force is concentrated over a small portion of the tube, there exists the possibility that the tube will be permanently deformed in this area and will lose the resiliency necessary to permit increased flow rates when the clamping force is removed.
Another desirable attribute in an adjustable tubing clamp is a dual mode of operation. In the first mode, actuation of a control member, typically a rotatable wheel or nut, rapidly closes the bore of the flexible tube until the point of flow regulation is reached, after which a given movement of the control element provides a much smaller degree of constriction in the flexible tubing, thus permitting extremely sensitive adjustment for precise regulation.
It is also desirable that a clamp of this type be capable of one-handed operation, leaving the other hand of the operator free for other functions, such as adjusting the position of a hypodermic needle through which the liquid is injected into a patient's vein. Finally, it is desirable that the clamp be inexpensive, in order to permit disposal after a single use, in keeping with preferred medical procedures.